An Introduction to Scientific Classification and Naming: Living organisms are assigned to groups based on their similarities. Domains are the largest classification category. Biologists assign organisms to one of three domains based on biochemical and genetic evidence. The three domains are Archea, Bacteria, and Eukarya. The full classification order for an organism is as follows: Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species. Living organisms are classified into
one of three domains.
These domains are Eukarya, Bacteria, and Archea. These three domains are divided into two
categories, depending on whether they contain prokaryotic or eukaryotic
organisms. Prokaryotes do not have a
membrane-enclosed nucleus; their genetic material is simply suspended in the cells . (A nucleus is
a membrane-bound organelle that holds the chromosomes; chromosomes contain the
genetic material that provides a blueprint for the organism itself). The prokaryotes
include both of the domains Bacteria and Archea. Bacteria are single-celled
microorganisms. Archea are bacteria-like
microorganisms that are found in extreme environments that are too harsh for
other forms of life (i.e. too hot, too salty, or too acidic).
Unlike prokaryotes, eukaryotes have cells that contain a
nucleus, and the overall cellular structure is much more complex than that
found in prokaryotes. The Domain Eukarya, is currently further classified into one of four Kingdoms: Plantae, Fungi, Protista, and Animalia.

Organisms usually have both common names and scientific names. The common name is the name we typically use to refer to an organism (i.e. Tufted Titmouse), while the scientific name is composed of the genus and species names. For example, the scientific name for the Tufted Titmouse is Baeolophus bicolor. You’ll notice that the correct form for writing a scientific name is to list the genus first and then the species. The name of the genus is capitalized, while the species name is written in all lower-case letters. Finally, the whole name is written in italics.

For human beings, the classification is as follows:

• Domain: Eukarya (cells with a nucleus)

• Kingdom: Animalia (multicellular, motile, ingests food)

• Phylum: Chordata (dorsal supporting rod and nerve cord)

• Class: Mammalia (hair, mammary glands)

• Order: Primates (adapted to climb trees)

• Family: Hominidae (adapted to walk erect)

• Genus: Homo (large brain, tool use)

• Species: sapiens

The scientific name can describe some physical aspect of the organism's appearance. For example, the Spring Peeper on the left (Pseudacris crucifer) is a small frog that gets its name because it has a x-, or crucifix-shaped, marking on its back.

The scientific names of some organisms are often derived from the name of the person who discovered it or someone they may know. The wildflower known as Twinleaf, shown at left, has the scientific name, Jeffersonia diphylla. The Twinleaf was named by a scientist in honor of his good friend, president Thomas Jefferson, who was amateur botanist. This was reported to be his favorite flower.

The scientific name can also be chosen based on the location where the organism was discovered such as the Tennessee Trillium (Trillium tennesseense). This is a particularly exciting species for me because my wife and I were the first to discover this flower. We found it during a plant walk on our property one day. When we could not locate the plant in any of our field guides or other reference materials, we contacted both the University of Tennessee and the Tennessee Native Plant Society regarding its identification. Following genetic testing and an analysis of anatomical structures, it was confirmed to be a new species. You can read the scientific article introducing the plant as a new species by clicking on this link.